Controlling Mash Temperature & Beer Calories: Mr. Wizard

Dear Mr. Wizard:

Just how critical is temperature control in all-grain brewing? I have recently built a basic three-tier all-grain system out of three converted kegs. I am in the Air Force, and currently stationed in England. Unfortunately, I must brew outdoors. This time of year the weather is cold, cloudy, windy, wet, and rainy especially on the weekends during my brewing sessions. I have brewed six 5-gallon batches (witbier, honey wheat, Trappist ale, ESB, brown ale, and a kölsch) and with every batch I have had a difficult time keeping my target temperature of 152° to 154° F. My temperatures bounce back and forth between 145° and 160° F. I usually hold my target temperature for 75 minutes of the 90-minute mash. When the temperature does fluctuate, I get it back to the target as quickly as possible.

The batches have turned out with a normal OG for their particular style, and they have tasted great. My goal is to constantly improve my brewing techniques and create the best brew possible. Should I be concerned with these temperature fluctuations? If so, do you have any suggestions for controlling the temperature in my battle with this wicked weather?

Marty Cowart
New Market, England

Mr. Wizard replies:

Mash temperature in all-grain brewing has a significant and demonstrable affect on beer flavor. In general, multi-temperature mash profiles incorporating temperature rests from 120* to 160* F will produce more fermentable worts than single temperature mashes held between 152* and 154* F. In flavor terms, beer produced from highly fermentable wort tends to be drier, crisper and perhaps lighter in body than those made from less fermentable worts. Another key difference is that alcohol content goes up with wort fermentability. I could go on and on about the "technical" differences in these sorts of beers and make an excellent argument for the importance of very precise temperature control. Indeed, these concerns are very real to commercial brewers because temperature control and the ability to repeat mash temperatures directly affect beer consistency. And consistency is one of the most important keys to commercial quality.

When homebrewers think of quality, we think of the sensory qualities of the beer. Does it taste, look and smell like intended on brew day? If it does, then all is great and we have a quality brew. However, if you only want to brew that one beer, then you should attempt to be as consistent as possible with your mash temperature, along with every other key variable in the brewing process. On the other hand, if you want to brew a wide assortment of great tasting homebrewed beer, I would not get overly concerned with your particular problem. It sounds to me that the mash stays in the desired range for most of the time and when it does cool off you heat it up in a reasonable time frame. I would be more concerned if you were getting the mash too hot and trying to cool it down because that destroys enzymes.

One easy solution to your problem is to insulate your mash tun. It sounds like you have a stainless-steel mash tun heated by a propane flame. You don’t want to insulate the bottom because the vessel would be difficult to heat if the insulation was doing its job and the insulation might burn (unless it is resistant to flame, like rock wool, glass fiber or, asbestos). If this were my project I would buy a non-flammable insulation material and insulate the sides of the mash tun and make some type of simple insulated, lid to prevent heat loss from the top. You could probably find these types of materials in your Air Force locker!

Dear Mr. Wizard:

One recent afternoon, over a few of our favorite beverages, a friend and I got into a good-natured argument. My friend is a diabetic (and a beer lover) so calorie and nutrition information is very important to him. We were debating just where the calories in beer come from. My friend’s opinion is that the alcohol provides the calories, based on the fact that a beer and a shot of liquor are considered equivalent. Having recently read the article on creating low calorie beers using "Beano," (April, 2001) I hypothesized that the majority of the calories in beer must come from unfermented carbohydrates. Please educate us.

Walter Scott
Reisterstown, Maryland

Mr. Wizard replies:

There is really no reason to argue about this because you are both partially correct. An average 12-ounce serving of a "domestic-style" beer contains about 14 grams of ethanol and 11 grams of carbohydrate. In caloric terms this equates to 98 kcals from ethanol and 44 kcals from the carbohydrate, for a total of 142 kcals. The most effective methods of making lower calorie beer involve reducing the alcohol content, residual carbohydrate or, most commonly, a combination of both. The article on using Beano to make a light beer focused on reducing the residual carbohydrates by increasing wort fermentability.

For more of Mr. Wizard's wisdom, see the latest issue of Brew Your Own now available at better homebrew shops and newsstand locations.

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